1. Field of Invention
The present invention relates to the removal of contaminating gases, such as oxygen, from containers. The present invention is particularly related to the removal of oxygen from containers for oxygen-sensitive products such as pharmaceuticals, biocompounds, chemicals, blood products, foods and beverages.
2. Description of the Background
Oxygen is a principal component of air and as such is of course pervasive in all locations exposed to the ambient atmosphere. Further, many materials are permeable in varying degrees to oxygen, so that containers made of such permeable materials cannot protect their contents from exposure to oxygen from the surrounding environment over prolonged periods of time. In many cases it is impractical or uneconomical to store oxygen-sensitive contents in containers made of oxygen-impermeable materials, so one must seek means for eliminating oxygen from permeable containers initially and then removing such oxygen as subsequently enters into the containers by permeation through the container walls before the oxygen can degrade the oxygen-sensitive contents. Unfortunately prior art means for oxygen scavenging have been impractical for many applications or have been of minimal effectiveness.
The oxygen sensitivity of pharmaceuticals and various biocompounds represents an issue of continued concern to drug manufacturers and others in the health care industry. Certain families of organic compounds commonly used for medicinal purposes are sensitive to oxygen and the resulting oxidation of these compounds contributes to the reduction of their usefulness. For example, the presence of oxygen in solutions of epinephrine result in a change from a colorless solution to a pink and eventually a brown colored solution or precipitate. Medical references advise that discolored solutions of epinephrine, as well as other medicinal compounds that undergo a color change with prolonged exposure to oxygen, should not be used for medical treatment. Further, prolonged exposure to oxygen can increase the photosensitivity of a drug. The antibiotics tetracycline and doxycycline undergo degradation when exposed to oxygen resulting in a drug that is potentially photo-toxic.
Medications are not the only products having sensitivity to oxygen. Blood and blood products, such as plasma, are particularly susceptible to oxidation by atmospheric oxygen, rendering them unusable. A simple method for the de-oxygenation of blood and blood products could prolong their storage life making blood bank and hospital supplies easier to maintain. Cosmetics formulated for topical application are prone to bacterial growth, aided by a rich oxygen environment. A storage means that limits the oxygen available to come in contact with the cosmetic formulation would not only increase the shelf life of the product but make it more hygienic for the user as well. Further, chemical additives currently used to prolong the storage life of cosmetics could be eliminated provided an alternate source for preservation of the formulation. Common food staples such as coffee, powdered milk, sugar, nuts, etc. are susceptible to spoilage when left exposed to the oxygen and moisture of the surrounding environment. An inexpensively manufactured, easily facilitated low oxygen-permeable plastic container could keep food staples stored, under vacuum, relatively free of oxygen to prevent spoilage and prolong shelf life.
Processed metals, such as comminuted metals that auto-ignite in air, and active catalysts like platinum on carbon carriers which need to be maintained in a reducing atmosphere, could benefit from a simple, low-cost means to remove oxygen from the containers they are held in. Many electric and electronic components are also susceptible to metal oxidation during their shipment and storage. This oxygen sensitivity is compounded by the fact that a vast majority of electronic devices are manufactured overseas and shipped to their destination via ocean going vessel, where exposure to sea air amplifies the potential for oxidation. The availability of oxygen free packaging would eliminate much of this destructive oxidation.
Current methods are available for the removal of oxygen from containers used for pharmaceuticals and other biologics during packaging however, most are cumbersome and costly and do nothing to maintain an oxygen-free environment over an extended period of time. One such process removes oxygen from the vial headspace over an oxygen-sensitive drug by flooding the environment with nitrogen or argon gas. Industrial filling equipment is available and capable of filing 20-30 vials per minute, leaving an oxygen level of slightly less than 1%. However, such equipment represents a large capital expenditure for the user which may make this method for oxygen removal less cost effective than some other means. In addition, this equipment does not provide for the elimination of oxygen that diffuses into the container during prolonged storage periods.
The addition of chemical preservatives that scavenge oxygen represents another method used to eliminate oxygen from medicinals and cosmetics. Antioxidants such as sodium bisulfite, sodium thiosulfates, phenol derivatives, methionine and, in the case of cosmetic formulations, hydroxyphenylglycerine are added to scavenge oxygen from the proximity of the oxygen-sensitive compound. However, these chemicals have a limited functional life and only scavenge oxygen at rates relative to their concentration, which diminishes over time. Further, because these chemical additives are actually an ingredient of the medicinal formulation, they are injected into the body along with the desired drug and may render the drug less effective, or worse, provoke additional health problems.
Current strategies for the elimination of oxygen from medicinal, cosmetic and electronics packaging are often cumbersome, costly, or potentially harmful. The need remains for a simple, cost effective method for the removal of oxygen from various kinds of packaging to enhance the storage life of oxygen-sensitive drugs, blood, blood products and substitutes, cosmetics, foods and beverages, electronic devices, and oxygen-sensitive metals.
Electrochemical oxygen separation systems, based on polymer electrolytes (ionomers) have been previously described by Maget, U.S. Pat. No. 5 3,489,670 and by Fujita et al., U.S. Pat. No. 4,539,086 and again by Fujita et al. in the publication, Journal of Applied Electrochemistry, 16 (1986), pp 935-940. The specific concept of combining small batteries with an electrochemical cell module has been described by Maget et al., U.S. Pat. No. 4,902,278. Maget, U.S. Pat. No. 4,902,278 also describes the use of a zinc-air battery as a power source.
While oxygen contamination as described above is a principal problem in many areas, other gaseous contaminants such as hydrogen and halogen gases are also candidates for elimination by electrochemical extraction.
Further, while in many cases the gaseous materials are present as deleterious contaminants, non-deleterious gaseous materials may be present in closed containers and be candidates for extraction because they are valuable materials in their own right or for other reasons.